Those cast bosses not drilled are how the 'truck' motors came, good clue. I have one of these motors but mine has the 'captains bars II' near the starter. But the main thing is checking the numbers as well as bore etc. Also these early 261 motors were not set up for full flow filtering, still had the bypass set up, I'd get that done. Should be info on this site or over on Inliners.org that shows how that's done.
Best of luck
